This invention relates to magnetic tape recording and reproducing machines, and, more particularly, to braking in such machines.
As is well known, a magnetic tape recording and reproducing machine comprises a rotating supply shaft for carrying a supply reel thereon, a rotating take-up shaft for carrying a take-up reel thereon, means for rotating the supply and take-up shafts, a magnetic head assembly for writing and reading information signals on and from a magnetic tape passing thereon, information input and output circuit means, means for maintaining the tape transporting speed constant and braking means to stop the rotation of the rotating supply and take-up shafts when the tape transporting is desired to be stopped.
A known braking mechanism is, a so called block brake mechanism, which comprises a brake drum carried on each rotating shaft for carrying a reel and a friction block which is pressed onto a peripheral surface of the brake drum upon braking.
There is known, a so called band brake mechanism which comprises a brake drum carried on each rotating shaft for carrying a reel and a band around the drum which binds the drum upon braking.
Another known brake system is an electromagnetic brake system, wherein D.C. current is supplied to the stator windings of the electric motor means for driving the supply and take-up reels.
In the play mode, tape transporting is stopped instantaneously when the brake mechanism is operated, because the tape transporting speed is slow. But when the machine is used in the rewinding mode or in the fact winding mode, it takes a time until the tape transporting stops after the brake mechanism is operated. It is very desirable to reduce the time from the operation of the brake mechanism to the stop of the tape. This stop time has been sufficiently reduced in the above mentioned known brake mechanisms for smaller reels, but has not yet been sufficient for larger reels.
In known magnetic tape recording and reproducing machines, the operator can start the machine or stop it arbitrarily. If he starts the machine in the play mode before stopping of the tape transporting has been effected after operating the brake mechanism to stop its rewinding, the tape may be broken. Accordingly, it is preferable to prohibit the machine from starting instantaneously after operating the same for stopping and until a complete stop of the tape has been achieved.